netdev - Re: iproute2 bug in json output for encap

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Date:   Fri, 14 Apr 2023 10:01:01 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Lars Ekman <uablrek@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: iproute2 bug in json output for encap

On Fri, 14 Apr 2023 18:26:03 +0200
Lars Ekman <uablrek@...il.com> wrote:

> Hi again,
> 
> Digging a little deeper I see that the double "dst" items will cause
> problems with most (all?) json parsers. I intend to use "go" and json
> parsing will be parsed to a "map" (hash-table) so duplicate keys will
> not work.
> 
> https://stackoverflow.com/questions/21832701/does-json-syntax-allow-duplicate-keys-in-an-object
> 
> IMHO it would be better to use a structured "encap" item. Something like;
> 
> [ {
>     "dst": "192.168.11.0/24",
>     "encap": {
>         "protocol": "ip6",
>         "id": 0,
>         "src": "::",
>         "dst": "fd00::c0a8:2dd",
>         "hoplimit": 0,
>         "tc": 0
>     },
>     "scope": "link",
>     "flags": [ ]
> } ]

Something like this?

diff --git a/ip/iproute_lwtunnel.c b/ip/iproute_lwtunnel.c
index 52221c6976b3..37730024caaf 100644
--- a/ip/iproute_lwtunnel.c
+++ b/ip/iproute_lwtunnel.c
@@ -834,14 +834,15 @@ static void print_encap_xfrm(FILE *fp, struct rtattr *encap)
 void lwt_print_encap(FILE *fp, struct rtattr *encap_type,
 			  struct rtattr *encap)
 {
-	int et;
+	uint16_t et;
 
 	if (!encap_type)
 		return;
 
 	et = rta_getattr_u16(encap_type);
-
-	print_string(PRINT_ANY, "encap", " encap %s ", format_encap_type(et));
+	open_json_object("encap");
+	print_string(PRINT_ANY, "encap_type", " encap %s ",
+		     format_encap_type(et));
 
 	switch (et) {
 	case LWTUNNEL_ENCAP_MPLS:
@@ -875,6 +876,7 @@ void lwt_print_encap(FILE *fp, struct rtattr *encap_type,
 		print_encap_xfrm(fp, encap);
 		break;
 	}
+	close_json_object();
 }
 
 static struct ipv6_sr_hdr *parse_srh(char *segbuf, int hmac, bool encap)